I'm looking for a new chain for the NX. The last one I bought only lasted about 5,000 miles. What can anyone recommend?

DID X-Ring... I went for the heavy duty "DID 520ZVM2" because Rocky Mountain ATV had them cheap at the time, not sure they still make them though... I did about 10,000 miles on it before I bought the Tenere and put the Dominator in storage, and it was still as good as new, I didn't have to adjusted it once after installation...

Things you probably already know:
It seems better to run the chain a little loose rather than a little tight, to avoid stretching...

Install a new chain with new sprockets, and since front sprockets are cheap it's worth changing it a couple of times over the life of the chain... (i.e. buy 2 (or 3) fronts, once it's showing some wear swap it for a new one, when that one is showing decent wear put the original one back on to finish it off)

Some people prefer not to lube, but I like to give the chain a good squirt before each long day ride, or each morning on multi-day trips....